Polymer dispersions, which can be polymer emulsions or polymer suspensions without a plasticizer, have conventionally been used for a wide array of applications, including, for example, as a protective, temporary film coating, as paint masking, as spray booth coating, for equipment protection, and for surface decontamination.
One conventional method for producing an emulsion of plasticized polymer-in-water involves mixing polymer, plasticizer, and surfactant to form a weld. The weld is then mixed while sufficient water is added to cause an inversion to a plasticized polymer-in-water emulsion or abbreviated oil-in-water emulsion (see, for example, U.S. Pat. No. 2,487,254). The oil-in-water emulsion can then, for example, be sprayed on a surface for which protection is desired, thereby forming a layer. After formation of the layer, water will readily evaporate or be absorbed into an adjacent fibrous layer, resulting in a continuous layer of polymer on the surface. This method, however, requires the input of a significant amount of energy, and further requires the use of relatively heavy duty equipment.
An improved version of the above-described method incorporates excess water in the initial mixing step, which results in plasticized polymer-in-water. Sufficient water is then slowly evaporated while mixing and heating, resulting in an inversion to water-in-oil plasticized polymer. Finally, water is added back, with mixing and heating, resulting in a reversion to a final oil plasticized polymer-in-water or an abbreviated oil-in-water emulsion (see, for example, U.S. Pat. No. 2,532,223). This method uses relatively low amounts of energy.
Other conventionally used methods of producing polymer dispersions include using an alkyl aryl alkali metal sulfonate agent and only a single inversion (see, for example, U.S. Pat. No. 2,611,755), as well as using a single inversion in combination with little or no plasticizer (see, for example, U.S. Pat. No. 3,234,161).
Various other methods of mixing and compounding polymeric materials have been reported, including methods that use screw extruders to mix polymeric compounds lacking water (see, for example, WO00/71608, U.S. Pat. No. 6,512,024, and WO00/71609) and screw extruders that mix polyol-based compounds (see, for example, U.S. Pat. No. 6,613,827 and WO02/28937).
Conventional methods, however, are time-consuming and energy intensive. What are needed in the art are methods and devices for rapid and economical production of polymer dispersions.